HLASM - BMR = Branch on Mixed / Minus Register

The opcode of the BMR extended mnemonic is X'07' with mask B'0100'.

The mask is the third hex digit of the instruction, and - though this is uncommon - can be regarded as the third hex digit of the opcode as well.

BMR is used both for Branch on Minus Register and for Branch on Mixed Register

Usage

  1. Perform a branch if the condition code is 1 or B'01', meaning either "minus" or "mixed".
  2. Condition code 1 may occur after bit operations, such as TM. After boolean operations (and, or, exclusive or) condition code 1 means mixed or all ones.
  3. Condition code 1 may also occur after signed binary calculations, such as AR. Do not use after multiplication or division, since these do not set the condition code.

Arguments

  1. Register holding the destination address.

Function

  1. The processor uses the PSW's two-bit condition code as an index into the 4-bit condition mask.
  2. If the selected mask-bit is one, then it branches to the address specified in the second argument. If the bit is zero, then the processor continues with the next instruction.
  3. The condition code does not change.

Special Cases

  1. If the destination address is in register 0 no branch will be taken.

Related Instructions

  1. BLR is a synonym for the BMR mnemonic.
  2. BM branches to a location that is directly addressable in base-displacement form.
  3. BCR is the real instruction associated with this extended mnemonic.

Hardware

  1. All hardware supports the BMR instruction.

Remarks

  1. The PSW's Amode setting determines how many bits are used for the destination address.

Examples

         YREGS                          * Define register names
         ...
         TM    FIELD,MASK               * Check bit settings
         BMR   R14                      * Ok, Return
         ...
         AR    R6,R1                    * Add to total
         BMR   R11                      * Go handle negative result
         ...

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